Place the chicken in a large stockpot with thyme, shallot, and celery. Cover the chicken with about 12 cups of water; use enough to fully submerge it. Add 3½ teaspoons salt. Bring to a boil. Reduce heat and simmer uncovered for 2 hours until the chicken is fully cooked.
Shred the chicken:
Turn the heat off. Using tongs, carefully transfer the chicken into a large bowl. Pick the meat from the bones once the chicken is cool enough to handle. You can add the skin to the soup if you like or discard it. Reserve the carcass for stock if you like.
Strain the broth into a large bowl through a fine mesh sieve. Wipe out the pot and return it to the stovetop. Discard the spent broth aromatics.
Make the soup:
Heat 1 tablespoon extra virgin olive oil in the pot over medium heat. Add the onion, carrots, and celery. Cook for 8–10 minutes. Season with salt. Add the garlic and scallion whites and cook for 1 minute until fragrant.
Add the ginger and turmeric and toss to coat. Cook for 1 minute until fragrant. Add the lentils and cook for 1 minute. Add a big pinch of salt.
Simmer the soup:
Pour in the reserved broth–you should have about 8–10 cups. Add the shredded chicken and bring to a boil. Reduce heat and simmer, uncovered, for 30 minutes until the lentils are tender. Taste and add crushed red pepper, salt, and pepper to taste. Stir in half the minced scallion greens and the lemon juice. Simmer for 5 minutes. Turn off the heat.
To serve:
Ladle the soup into bowls. Garnish with the remaining minced scallion greens. Enjoy!